The distinction between multifocal motor neuropathy, treatable by intravenous immunoglobulins (IVIg), and degenerative motor neurone disorders is often difficult. To find predictive factors for the response to IVIg treatment, 40 consecutive patients with pure lower motor neurone disorders (LMND) were prospectively examined. They all received at least two times IVIg (2 g/kg bodyweight). Prior to the first and before all the following treatments a standardized evaluation was performed including clinical examination, neurophysiological and laboratory evaluation. According to changes in the neurological examination and the Neuromuscular Symptom Score, the patients were divided into responders and non-responders after the second course of treatment. In our study, no single clinical, neurophysiological, or laboratory parameter was sensitive enough to predict response. The only single parameter that highly correlated with a positive response to treatment was an elevated GM1 antibody titre. Lack of response to IVIg treatment is likely in patients with generalization of electromyographic signs of denervation beyond the clinically involved site, proximal localization of the weakness, and an elevated level of the creatinekinase. Conduction blocks do not distinguish between both groups. We propose a scoring system combining clinical, serological and neurophysiological data in order to decide which patients with LMND may receive IVIg.